Movements and Demographic Factors Limiting Recovery of Endangered Koloa Maoli (Hawaiian Duck)

Science Center Objects

USGS and Oregon State University (OSU) have joined forces to support USFWS with research needed help manage and recover the endangered Hawaiian duck, locally known as koloa maoli.  Hybridization of koloa with feral Mallards on O‘ahu and Maui is believed to have resulted in complete introgression in those populations (Engilis et al. 2002), and Kaua‘i is the only island that likely supports a viable population of pure koloa.  Kaua‘i Island supports approximately 90% of the remaining true koloa, and Hanalei National Wildlife Refuge (NWR) and the surrounding taro agriculture of the north shore of Kaua‘i is the most important region for koloa on Kaua’i (USFWS 2005).  Beginning in 2010, Kaua‘i NWRC, in cooperation with OSU, initiated a priority recovery action to begin removing hybrids from the population of koloa on the refuge.  This adds to recent research that used genetic analysis to develop a morphological key for identifying hybrids when captured in the field (Uyehara 2007, Fowler et al. 2008). 

Koloa maoli

Koloa maoli. Photo: B. Zaun

Overview: 

USGS and Oregon State University (OSU) have joined forces to support USFWS with research needed help manage and recover the endangered Hawaiian duck (Anas wyvilliana), locally known as koloa maoli.  Hybridization of koloa with feral Mallards on O‘ahu and Maui is believed to have resulted in complete introgression in those populations (Engilis et al. 2002), and Kaua‘i is the only island that likely supports a viable population of pure koloa.  Kaua‘i Island supports approximately 90% of the remaining true koloa, and Hanalei NWR and the surrounding taro agriculture of the north shore of Kaua‘i is the most important region for koloa on Kaua‘i (USFWS 2005).  Beginning in 2010, Kaua‘i NWRC, in cooperation with OSU, initiated a priority recovery action to begin removing hybrids from the population of koloa on the refuge.  This adds to recent research that used genetic analysis to develop a morphological key for identifying hybrids when captured in the field (Uyehara 2007, Fowler et al. 2008).   No research has been conducted for understanding habitat use or quantifying vital rates (e.g., survival) needed to identify demographic bottlenecks.  Daily movements between foraging, loafing, and roosting sites have been reported (Perkins 1903, Giffin 1983) and recent results from a pilot project using satellite radio transmitters have confirmed koloa movements between Kaua‘i and Ni‘ihau; however, the extent, individual variability of these movements are unclear.  Furthermore, the significance and relationship of daily and seasonal movement patterns to various aspects of koloa life history (e.g., breeding and molting) are not understood.  Absent information on these critical aspects of species biology, it is difficult to identify the scale needed for conservation actions (e.g., predator control, hybrid removal, and habitat management and restoration) and effective recovery of koloa is not possible.

The Hanalei NWR and Hulēia NWR Draft Comprehensive Conservation Plan (CCP) includes research objectives aimed specifically at koloa recovery including Objective 4.2- Conduct high priority research projects to evaluate hybridization threats to koloa, identify factors most limiting koloa population recovery, and investigate koloa daily and seasonal movements.  For effective management, USFWS seeks information on these critical aspects of koloa biology.

Project Objectives:

The primary objectives of the research are to conduct field trials of current and alternate bird sampling methods and to estimate and compare the precision of current and alternate sampling methods based on specific monitoring objectives. Other important objectives are to compare logistical, ecological, and cultural advantages and disadvantages of current and alternative survey methods and from these studies develop protocols for survey methods and data analyses.

The project goals are aligned with the priorities of the USGS Ecosystems Science Strategy in that the research will increase the understanding of the population status and trends of federally endangered bird species by DOI agencies. Additionally, results of analyses of survey data will help DOI and other managers identify the factors driving species declines and will assist them in evaluating tradeoffs involved in conservation and land use strategies.